Selecting

The seeds formed on the crossing-parents are harvested extremely carefully. Each seed could be the beginning of a new, successful variety. The progeny of the crossings can show all possible combinations of the characteristics of both parents. The breeder tries to find those plants which have the best combination of desirable characteristics. These characteristics then have to be fixed in a variety, i.e. all plants of the variety have to uniformly exhibit these characteristics.



Generation cycle
Fixing of the genetic splitting, made during the crossings, into lines and varieties which are uniform and stable, usually takes 6 to 8 generations. The generation cycle is, therefore, a major factor in the timescale of creating a new variety. With some crops, lettuce for instance, it is possible to select more than one generation per year. The development of a new variety can then be relatively rapid but will still take 4 to 6 years.

Biennial crops
Much longer is the timescale for biennial crops. These are crops, like carrots and cabbage, which do not flower and produce seed until the second year after sowing. That is why developing a new carrot variety can take as long as 12 to 15 years.

Hybrids and non-hybrids
Nowadays, most vegetable varieties are hybrids which are identified with the ‘F1’ code. Hybrids are created by crossing two uniform, inbred parent lines. Some advantages of hybrids are: uniformity, precocity and higher production. Breeders are also often able to combine resistances more easily in hybrid varieties so that they can react quickly to any new diseases occurring.

It is not yet possible to make hybrids in all crops. Two examples of non-hybrid vegetable crops are lettuce and beans.

The result: one handful of seeds
After years of breeding and selecting in the selection fields of Rijk Zwaan, the result is one handful of seeds of a promising variety. But will this variety fulfil expectations in practice? That is why, subsequently, variety trials are carried out by commercial growers under practical conditions, and maybe in a glasshouse, a polytunnel or outdoors. In these variety trials the new varieties are always compared with existing varieties. These existing varieties set the standards. When the results of the variety trials are positive, large-scale production of the new varieties can begin.